1 // xtrcrypt.cpp - originally written and placed in the public domain by Wei Dai
2
3 #include "pch.h"
4
5 #include "asn.h"
6 #include "integer.h"
7 #include "xtrcrypt.h"
8 #include "nbtheory.h"
9 #include "modarith.h"
10 #include "argnames.h"
11
NAMESPACE_BEGIN(CryptoPP)12 NAMESPACE_BEGIN(CryptoPP)
13
14 XTR_DH::XTR_DH(const Integer &p, const Integer &q, const GFP2Element &g)
15 : m_p(p), m_q(q), m_g(g)
16 {
17 }
18
XTR_DH(RandomNumberGenerator & rng,unsigned int pbits,unsigned int qbits)19 XTR_DH::XTR_DH(RandomNumberGenerator &rng, unsigned int pbits, unsigned int qbits)
20 {
21 XTR_FindPrimesAndGenerator(rng, m_p, m_q, m_g, pbits, qbits);
22 }
23
XTR_DH(BufferedTransformation & bt)24 XTR_DH::XTR_DH(BufferedTransformation &bt)
25 {
26 BERSequenceDecoder seq(bt);
27 m_p.BERDecode(seq);
28 m_q.BERDecode(seq);
29 m_g.c1.BERDecode(seq);
30 m_g.c2.BERDecode(seq);
31 seq.MessageEnd();
32 }
33
DEREncode(BufferedTransformation & bt) const34 void XTR_DH::DEREncode(BufferedTransformation &bt) const
35 {
36 DERSequenceEncoder seq(bt);
37 m_p.DEREncode(seq);
38 m_q.DEREncode(seq);
39 m_g.c1.DEREncode(seq);
40 m_g.c2.DEREncode(seq);
41 seq.MessageEnd();
42 }
43
Validate(RandomNumberGenerator & rng,unsigned int level) const44 bool XTR_DH::Validate(RandomNumberGenerator &rng, unsigned int level) const
45 {
46 bool pass = true;
47 pass = pass && m_p > Integer::One() && m_p.IsOdd();
48 CRYPTOPP_ASSERT(pass);
49 pass = pass && m_q > Integer::One() && m_q.IsOdd();
50 CRYPTOPP_ASSERT(pass);
51 GFP2Element three = GFP2_ONB<ModularArithmetic>(m_p).ConvertIn(3);
52 CRYPTOPP_ASSERT(pass);
53 pass = pass && !(m_g.c1.IsNegative() || m_g.c2.IsNegative() || m_g.c1 >= m_p || m_g.c2 >= m_p || m_g == three);
54 CRYPTOPP_ASSERT(pass);
55 if (level >= 1)
56 {
57 pass = pass && ((m_p.Squared()-m_p+1)%m_q).IsZero();
58 CRYPTOPP_ASSERT(pass);
59 }
60 if (level >= 2)
61 {
62 pass = pass && VerifyPrime(rng, m_p, level-2) && VerifyPrime(rng, m_q, level-2);
63 CRYPTOPP_ASSERT(pass);
64 pass = pass && XTR_Exponentiate(m_g, (m_p.Squared()-m_p+1)/m_q, m_p) != three;
65 CRYPTOPP_ASSERT(pass);
66 pass = pass && XTR_Exponentiate(m_g, m_q, m_p) == three;
67 CRYPTOPP_ASSERT(pass);
68 }
69 return pass;
70 }
71
GetVoidValue(const char * name,const std::type_info & valueType,void * pValue) const72 bool XTR_DH::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
73 {
74 return GetValueHelper(this, name, valueType, pValue).Assignable()
75 CRYPTOPP_GET_FUNCTION_ENTRY(Modulus)
76 CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupOrder)
77 CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupGenerator)
78 ;
79 }
80
AssignFrom(const NameValuePairs & source)81 void XTR_DH::AssignFrom(const NameValuePairs &source)
82 {
83 AssignFromHelper(this, source)
84 CRYPTOPP_SET_FUNCTION_ENTRY(Modulus)
85 CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupOrder)
86 CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupGenerator)
87 ;
88 }
89
GeneratePrivateKey(RandomNumberGenerator & rng,byte * privateKey) const90 void XTR_DH::GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const
91 {
92 Integer x(rng, Integer::Zero(), m_q-1);
93 x.Encode(privateKey, PrivateKeyLength());
94 }
95
GeneratePublicKey(RandomNumberGenerator & rng,const byte * privateKey,byte * publicKey) const96 void XTR_DH::GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const
97 {
98 CRYPTOPP_UNUSED(rng);
99 Integer x(privateKey, PrivateKeyLength());
100 GFP2Element y = XTR_Exponentiate(m_g, x, m_p);
101 y.Encode(publicKey, PublicKeyLength());
102 }
103
Agree(byte * agreedValue,const byte * privateKey,const byte * otherPublicKey,bool validateOtherPublicKey) const104 bool XTR_DH::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const
105 {
106 GFP2Element w(otherPublicKey, PublicKeyLength());
107 if (validateOtherPublicKey)
108 {
109 GFP2_ONB<ModularArithmetic> gfp2(m_p);
110 GFP2Element three = gfp2.ConvertIn(3);
111 if (w.c1.IsNegative() || w.c2.IsNegative() || w.c1 >= m_p || w.c2 >= m_p || w == three)
112 return false;
113 if (XTR_Exponentiate(w, m_q, m_p) != three)
114 return false;
115 }
116 Integer s(privateKey, PrivateKeyLength());
117 GFP2Element z = XTR_Exponentiate(w, s, m_p);
118 z.Encode(agreedValue, AgreedValueLength());
119 return true;
120 }
121
122 NAMESPACE_END
123